Originally Posted by kladue
Not a good idea to operate near the trip point on the breaker, better to be operating at 80% maximum rating on a continuous basis because of heating inside breaker and enclosure. Here is a link to a page describing why that is standard practice http://ecmweb.com/mag/electric_sizing_circuit_breaker/
I firmly believe this is a piece of information that is severely distorted in many ways. The link posted quotes the supposed NEC info that does not exist in the current NEC code. The post you quoted was from 1996 and it in now 2011 with many code changes in between.
Another thought: The 80% rule, often quoted, applies to multi drop outlet circuits. It does NOT apply to a single drop outlet, i.e. a single circuit outlet for a dryer, range or some other single outlet receptacle. With a single outlet circuit, the current draw can be at or near the limit of the breaker without issue, standard breaker or
GFCI. Also, the 80% rule in the code applies to the architect, builder and the electrician ......it does not apply to the home owner using his home. It is a design and build issue.
You would expect an "electrician" to know their stuff, but, a lot of them do not. Info is frequently pulled out of their - - never mind.
BTW, do you have the current NEC code manual?
You want to learn more? Do a check up on Arc Fault Breakers. Or, for that matter, check on today's code for GFCI circuits and where they must
be implemented. Things have changed dramatically - but - a lot of them do not apply unless the facility has been wired since the particular code change was implemented.
For example: You have a home that was wired in 1938. Is knob and tube wiring in it ok today?
Rant over - I'm done.